Updated Jan 27, 2007 by farcepest
Labels:	Featured, Documentation

RecordTypes

Description of record types and results

Introduction

adns supports several DNS record types, in both raw and "cooked" formats. These all come from adns.rr (resource records). Generally the "cooked" formats may require several internal queries and return additional information. All queries return data in a tuple as (status, CNAME, expires, answer), where:

status: status code from adns.status
CNAME: CNAME of the answer; if the target was not a CNAME, this will be None
expires: When the answer expires, in UNIX ticks
answer: The answer to the query

The format of answer varies depending on the type of query/record. Since DNS queries should be assumed to return multiple answers, answer is always a sequence (tuple) of resource records.

Record Types and Answers

In all examples below:

>>> import adns
>>> c=adns.init()

A

Returns the IP address of the target.

>>> c.synchronous("www.google.com", adns.rr.A)
(0, 'www.l.google.com', 1167604334, ('216.239.37.99', '216.239.37.104'))

ADDR

Like A, but returns 2-tuples of the address family and IP address:

>>> c.synchronous("www.google.com", adns.rr.ADDR)
(0, 'www.l.google.com', 1167604334, ((2, '216.239.37.104'), (2, '216.239.37.99')))

Note that 2 is the address family for IPv6, though these are IPv4 addresses. (Address families are defined in RFC 1700.) So why is it 2 and not 1?...

http://www.iana.org/assignments/address-family-numbers

CNAME

Returns the CNAME (if any) of the target:

>>> c.synchronous("www.google.com", adns.rr.CNAME)
(0, None, 1167864839, ('www.l.google.com',))

Note the CNAME field of the result tuple will probably always be None, unless the CNAME points to another CNAME, which is officially discouraged by the RFCs.

TXT

Returns a tuple of strings:

>>> c.synchronous("google.com", adns.rr.TXT)
(0, None, 1167605128, (('v=spf1 ptr ?all',),))

MXraw

Returns MX records as (priority, hostname):

>>> c.synchronous("gmail.com", adns.rr.MXraw)
(0, None, 1167608363, (
  (5, 'gmail-smtp-in.l.google.com'),
  (10, 'alt1.gmail-smtp-in.l.google.com'),
  (10, 'alt2.gmail-smtp-in.l.google.com'),
  (50, 'gsmtp163.google.com'),
  (50, 'gsmtp183.google.com')))

MX

Like MXraw, but resolves all the hostnames. Each hostname is returned as (hostname, status, ADDR) where ADDR is a sequence of ADDR return values:

>>> c.synchronous("gmail.com", adns.rr.MX)
(0, None, 1167605059, (
  (5, ('gmail-smtp-in.l.google.com', 0, ((2, '209.85.133.27'), (2, '209.85.133.114')))), 
  (10, ('alt1.gmail-smtp-in.l.google.com', 0, ((2, '64.233.167.114'), (2, '64.233.167.27')))),
  (10, ('alt2.gmail-smtp-in.l.google.com', 0, ((2, '64.233.183.27'), (2, '64.233.183.114')))),
  (50, ('gsmtp183.google.com', 0, ((2, '64.233.183.27'),))),
  (50, ('gsmtp163.google.com', 0, ((2, '64.233.163.27'),)))))

NSraw

Returns NS records as hostnames:

>>> c.synchronous("gmail.com", adns.rr.NSraw)
(0, None, 1167676668, ('ns3.google.com', 'ns4.google.com', 'ns1.google.com', 'ns2.google.com'))

NS

Like NS,but resolves all the hostnames. Each hostname is returned as (hostname, status, ADDR) where ADDR is a sequence of ADDR return values:

>>> c.synchronous("gmail.com", adns.rr.NS)
(0, None, 1167676668, (
  ('ns1.google.com', 0, ((2, '216.239.32.10'),)),
  ('ns2.google.com', 0, ((2, '216.239.34.10'),)),
  ('ns3.google.com', 0, ((2, '216.239.36.10'),)),
  ('ns4.google.com', 0, ((2, '216.239.38.10'),))))

SOA and SOAraw

Returns the SOA record.

>>> c.synchronous("gmail.com", adns.rr.SOA)
(0, None, 1167691858, (
  ('ns1.google.com', 'dns-admin@google.com', 2006120100, 21600, 3600, 1209600, 300),))
>>> c.synchronous("gmail.com", adns.rr.SOAraw)
(0, None, 1167691862, (
  ('ns1.google.com', 'dns-admin.google.com', 2006120100, 21600, 3600, 1209600, 300),))

The only difference is that SOAraw returns the unmolested contact field and SOA changes the first period in the contact field to an @ sign so that it is immediately useful as an e-mail address.

The values are these tuples are described in detail in RFC 1035. Also see http://www.zytrax.com/books/dns/ch8/soa.html

SRV and SRVraw

Returns SRV records as (priority, weight, port, hostname):

>>> c.synchronous("_kerberos._tcp.example.com", adns.rr.SRVraw)
(0, None, 1167606966, ((1, 0, 88, 'krb1.example.com'),))

SRV, like MX, resolves all hostnames, whereas SRVraw does not.

SRV reccords are described in RFC 2052.

HINFO

These are "host info" records, which are rarely seen on the internet, due to being a security exposure.

RP and RPraw

These are "responsible person" records. Like HINFO, they are rarely seen on the internet.

Comment by chaz6.com, Jun 16, 2009

How does one use a different class - for example CHAOS instead of INTERNET (IN)?

Comment by mdomsch, Aug 23, 2009

Note for ADDR lookups, the address family portion returns '2' for IPv4 addresses because this value is the traditional /usr/include/linux/socket.h value for AF_INET. This value should be '10' for IPv6 (AF_INET6) addresses.